Abstract

South Rewa basin of Central India is one of the poorly understood sedimentary basins in the world with potential hydrocarbon bearing sub-trappean Gondwana sediments deposited in a typical rift environment followed by masking due to basalt flows related to the Deccan volcanism (~ 65 Ma). To delineate the sub-trappean Gondwana sediments infested with several dykes and sills along with the basement configuration and complex subsurface geological structures, we have derived pre-stack depth migration (PSDM) seismic image with tomographic velocity model obtained along the 127 km long common-depth-point (CDP) seismic reflection data acquired for the N-S trending KuvariShahdol profile in the Rewa basin. The stack section obtained using conventional velocity analysis and seismic data processing fails to provide good result as well as the pre-stack time migration (PSTM) although show some improvement but could not able to image the complex geological structures in this sedimentary basin. Hence, a robust tomographic velocity modeling approach being adopted to image the fine-scale subtle subsurface geological structures with smooth velocity variations, which clearly depicts the presence and extension of basaltic trap with numerous dyke intrusions, alternate horst and grabens with deposition of thick (>5.0 km) hydrocarbon bearing Gondwana sediments overlained by highly heterogeneous basalts (< 2.0 km thick). The PSDM image shows all the subsurface geological structures corroborated with the tomographic velocity model indicating highly fractured basement interspersed by Gondwana sediments due to intense tectonic activity in this rift basin. The seismic image is well constrained in which all the reflection events are flattened having minimum residual moveout (RMO) in the image gathers obtained with the help of tomographic imaging using constrained velocity inversion (CVI) and pre-stack depth migration. The presence of numerous faults cutting across the Gondwana sediments deposited with alternate horst and graben structures and basement undulations with fractures facilitate as the conduits for the emancipation of volcanic lavas forming dykes and sills in this region, which are considered as lower crustal mafic rocks due to the Deccan volcanism.